ASTRONOMICAL NOTES

Grey River Argus, 23 May 1941, Page 6

ASTRONOMICAL NOTES

A METEOR DISPLAY. (By “Random Observer.”) A press item the other day .featured a meteor display on the night of Monday, May 5, recording the falling of numbers of bright and highlycoloured shooting stars between midnight and dawn. These meteors were actually portion of the debris left behind by Halley’s Comet on its last visit 31 years ago. This shower recurs annually in the early days of May. CELESTIAL “TRACER” BULLETS. In 1799, 1833 and 1866 wonderful showers of shooting stars appeared in the heavens, due to the precision with which the earth in its orbit met and ploughed through a certain meteor swarm, the Leonids. Though only on rare occasions may such a sight be seen, on almost every line night occasional “shooting stars” can be seen speeding through the sky. The term “shooting star” is a misnomer. Actually meteors are merely small stony or metallic bodies in swarms traveling in orbits which may happen to intersect the earth’s path at some point. If the swarm is near the earth at the critical time, some of the particles are intercepted by the upper atmosphere, and rushing through at an average speed of 27 miles a second, they are heated by friction' to a few thousand degrees, rendered incandescent, and usually completely vaporised, all within a few seconds. The larger meteors naturally light up vividly, and are known as fire-balls. They sometimes explode with very spectacular results. Those that reach the earth are called meteorites. Specimens of these are housed in many museums, and good sums are usually paid for authentic specimens. “BLITZKREIG” AVERTED. But for our blanketing atmosphere, which acts as the perfect body-belt, we would be bombarded out of existence by falling meteors, as millions of these objects are intercepted yearly by our earth. We 'would have “Buckley’s chance” with a moulting chicken in a hailstorm were it not otherwise. A much slower speed would . fail to cause combustion and make the small missile a “blitzer.” As it is, a certain number get through. In Arizona is a huge crater considered to have been dug by a monster meteorite that hit there long ago, and perhaps some day science may be able to excavate it from a great depth. Then in 1908 the devastation of a large slice of forest in Siberia for many mlies was attributed to the blast of a meteor’s impact. And a couple of years ago one heard on the Japanese radio an account of a meteorite, the size of- a man’s head, that crashed into a dwelling with occupants. The absence of any atmosphere on the moon means that it must get the full force of whatever meteors collide with it, and at 27 miles a second a few millions can do a lot of pockmarking on its already much-scarred surface. ONE OF THE “WHOPPERS.” On August 14th last, at 5.37 a.m., a brilliant meteor was seen all over the North Island, and Mr. R. A. McIntosh, Director of the Meteor Section, deduced its path from about eighty reports. It first became luminous 20 miles south-west of the mouth- of the Waikato, at a height of 109 miles. It moved almost due east, passing over Rangiriri and Waihi, finally disappearing 20 miles due north of Cape Runaway, its height then being only 20 miles. It had covered 227 miles in twelve seconds, revealing a velocity through the atmosphere of 19 a second. Some good observing must have been done on that occasion.

Early in February a brilliant meteorite was reported in Canterbury, and at the time of the Great Aurora three months ago South Taranaki had one.

THE COMET THAT “SCUTTLED” ITSELF.

The theory that the heads ot

> comets are actually swarms of meteors is supported by the history oi a certain remarkable comet known as Biela’s Comet. In January, 1846, the comet was seen to divide into two parts. At its next appearance, in 1852 the division between the parts had greatly increased. In 1858-59, when it was again due, it had disappeared. Another appearance had been calculated for 1872. but the comet still refused to appear. What did occur was a magnificent display of meteors, and it was found that the orbit of this of meteors was the same as the orbit of the vanished comet. This fact certainly seems to indicate that the comet was in whole or part composed of meteors. Comets sooner or later disintegrate, and. becoming derelict, stream around the sun as invisible meteor swarms, moving in closed almost circular orbits instead of their former highly elliptical paths. It is computed that there are about 120,000 .comets altogether in our solar system, and the number of meteor swarms is countless. By meteor observation amateurs are yearly adding to our knowledge of the various swarms. In a’ subsequent article the practical observation of meteors will be discussed.